1. Field of the Invention
The present invention relates to aqueous dispersions of copolymers and/or graft copolymers composed of ethylenically unsaturated perfluoroalkyl monomers and perfluoroalkyl-free ethylenically unsaturated monomers, prepared by polymerisation in the presence of aqueous, emulsifierfree polyurethane dispersions as the graft base based on compounds containing perfluoroalkyl groups and active hydrogen atoms and compounds containing ionic and/or nonionic hydrophilic groups and active hydrogen atoms and polyisocyanates.
Preferred ionic groups are salt groups.
2. Description of the Related Art
Aqueous copolymer dispersions based on monomers containing perfluoroalkyl groups are known. They produce good oil-repellant finishes on many substrates as long as the perfluoroalkyl radicals are linear and contain at least 6 C atoms. When these copolymer dispersions are prepared by emulsion polymerisation, emulsifiers or emulsifier systems are used. Depending on the emulsifier system, anionically or cationically stabilised dispersions whose pot life can be improved by adding nonionic emulsifiers are obtained. Cationic perfluoroalkyl(meth)acrylate copolymer dispersions, also in combination with further finishing agents or textile auxiliaries, are particularly suitable for the oil-repellent finishing of textiles and carpets.
The effectiveness of the oil-repellent finishing agents based on polyperfluoroalkyl(meth)acrylate dispersions is largely dependent on the concentration of perfluoroalkyl groups in the copolymer, on the composition of the copolymer and on its particle size.
The type of emulsifiers used also affects the properties in practical applications. For practical applications, it is often necessary that the oil-repellent finish is additionally accompanied by a water-repellent finish.
Processes for preparing aqueous dispersions of graft copolymers are known. Graft copolymerisation using perfluoroalkyl(meth)acrylates in aqueous dispersion is described, for example, in DE-OS (German Published Specification) 3,407,361. The use of aqueous polyurethane dispersions as the graft base is explained in DE-OS (German Published Specification) 3,407,362, 1,953,345 and 1,953,349.